It's definitely a bright set. When watching HDR10 with the Brightness set at max, the television seems to handle perceptive contrast very well. I can tell that the black bars aren't as deep and inky as they would be on something like the Q9FN. I'm astonished, actually, that SDR has to be dialed in to 10 while HDR10 looks fantastic at max. Dolby Vision also looks fairly bright on a low brightness... I can't imagine cranking that mode up (it was streaming from VUDU).
And there's definitely light bleeding into the bars when there's bright content near them. I tried to get a picture, but what I captured does not reflect how it actually looks in person. But yeah, I understand what the OP meant before when it looks great most of the time but once in a while it may show up in a negative way if in a dark environment... and my environment is dark. I was able to use the TV box to cover about 3/4 of the egress window in my basement here so... fairly dark. Tonight will be the true test. If the blooming is something you're extremely sensitive to, I guess don't get the Z9F, but it's not as bad as the hyperbole police have tried to make people believe without seeing it for themselves.
With ACTUAL CONTENT, I'll say it's not really all that bad... it treats overlay stuff it seemingly doesn't anticipate too well though. With my Sony X800, when I pause a movie and the icon appears in the bottom left hand corner to confirm I've paused the film, the bloom there is absolutely awful. It. Lights. Up. Big time. That's because of the maximum brightness cranked up for HDR10, of course. But I'm not actually getting that kind of bloom while doing torture test stuff from The Matrix, Alien Covenant, etc. Bloom/bleed, yes, but it's honestly comparable to what I've had with my 2016 M Series Vizio.
Before you freak out about that, though, the Sony chip really does seem to handle blooming in a better way than my old TV did. For example, when playing Cuphead, you get a loading screen that's not gray but not exactly black either, has simulated old-school animation film grain caked on, and a hand drawn hourglass figure jumping in the bottom right hand corner. I used to see a very large light halo around that hourglass on my old Vizio... but not so on the Z9F. It blends in very well with the rest of the picture, as is appropriate. The television's processing really seems to be holding the brunt of the weight here in regards to contrast... and it does a damn good job, all things considered when it comes to the measured specs.
When I first booted up Sea of Thieves on my Xbox One X and saw the opening map scroll cinematic, I thought I could detect what could have possibly been a HINT of DSE... but it came and went so fast that I can't tell if it was the game and how the cinematic looked or if it was the television. I've been looking at stuff that screamed DSE on my old Vizio and still can't really find any issues whatsoever. Another torture test compared to my old TV was a scene where Charlie Brown's sister in the Peanut's Movie was on stage... that green curtain in the background wreaked havoc on my old set, but not here. The challenge temples in Zelda: Breath of the Wild was another 'oh my god I HATE this' thing in regards to DSE on my old set... clean on the Z9F.
So there's positives and negatives to this set... it seems to do what it wants to do quite well and you can throw it a curveball on occasion that makes it behave in a shocking and negative way, but yeah, actual content seems to be fine once you fine tune the settings to your liking for SDR and HDR. Personally, the brighter nits and better HDR and having wide color really makes this television a world of difference from my Vizio. Gaming is responsive and just looks bonkers too, and I'm not seeing too many negatives while sampling stuff from 4K HDR films.
So I've done dark content with contrast, I've seen mostly white imagery with dark contrast laced throughout, I've seen CGI animation, solid animation (South Park, Adventure Time), I've seen some games... not a bad day so far, all in all. Might take a break to mow the lawn. Boo.